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Set spatial derivatives to zero as boundary conditions
Posted 20 juil. 2016, 04:57 UTC−4 Structural Mechanics Version 5.1 0 Replies
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I am trying to model the prestressed eigenfrequencies of a rectangular cross section beam. I aim to "hold" the beam in three locations, so we can define 5 points along it at x=-l/2-l0, -l/2, 0, l/2 and l/2+l0. Where l0 is the length of the ends of the beam, and l is the length of the middle portion of the beam, and it is held at positions x=-l/2, 0 and l/2. Initially, I thought the "pinned" constraint would be sufficient for these three locations, however, the eigenfrequency solution is producing results I thought this boundary condition would eliminate.
Ideally, I wish to define u(x=-l/2,0,l/2)=0 (that's easy) but also that d^2u/dx^2(x=-l/2,0,l/2)=0, i.e. the second SPATIAL derivative of displacement is equal to zero. All of the available point constraints available to me can only set displacement or TIME derivates of displacement.
How can I set these three points spatial derivatives to be equal to zero?
Thank you in advance if you can offer me any suggestions.
Hello Jeremy Bourhill
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